Vortex pumps

ABSTRACT

A vortex pump casing has a generally toroidal inner wall of constant cross-sectional radius with a cylindrical axially offset impeller recess intersecting the toroidal wall. The toroidal wall is actually a volute and the impeller recess intersects the volute at an obtuse angle that increases progressively from the maximum major radius of the volute to the minimum (cutwater) major radius of the volute. Formulae for various design features, including the impeller vane depth, the radius to the volute cutwater, the impeller diameter, and the optimum number of impeller blades are presented, based on the diameter of the inlet port of the volute.

'nited States atent [1 1 Kempi VORTEX PUMPS [75] Inventor: Dennis D. Kempi, San Jose, Calif.

[73] Assignee: FMC Corporation, San Jose, Calif.

[22] Filed: June 14, 1972 i [21] Appl. No.: 262,913

- Related US. Application Data [63] Continuation-impart of Ser. No. 104,315, Jan. 6,

[52] US. Cl. 415/213 A, 415/206, 415/219 C [51] Int. Cl. F04d 29/44, F04d 7/00 [58] Field of Search 415/204, 206, 213, 415/213 A, 219 C [56] References Cited UNITED STATES PATENTS 2,785,930 3/1957 Burnside 415/213 A 2,958,293 11/1960 Pray, Jr.. 415/213 A 3,167,021 1/1965 Sence.... 415/213 A 3,130,679 l/1964 Sence.... 415/213 A 3,171,357 3/1964 Egger 415/206 3,269,325 8/1966 Schwed et al.. 415/213 A 3,316,848 5/1967 Egger 415/204 G6 as e4 1 a J Sept. 18, 1973 3,319,573 5/1967 Judd 415/213 A 3,384,026 5/1968 Williamson, Jr. 415/204 FOREIGN PATENTS OR APPLICATIONS 390,688 8/1965 Switzerland 415/213 A 1,006,340 4/1957 Germany 415/213 A Primary Examiner-#I-lenry F. Raduazo Attorney-F. W. Anderson et a1.

[57] ABSTRACT I A vortex pump casing has a generally toroidal inner wall of constant-cross-sectional radius with a cylindri cal axially offset impeller recess intersecting the toroidal wall. The toroidal wall is actually a volute and the impeller recess intersects the volute at an obtuse angle that increases progressively from the maximum major radius of the volute to the minimum (cutwater) major radius of the volute. Formulae for various design features, including the impeller vane depth, the radius to the volute cutwater, the impeller diameter, and the optimum number of impeller blades are presented, based on the diameter of the inlet port of the volute.

15 Claims, 18 Drawing Figures PATENTEI] SEP 1 '8 I975 SHEET 1 UP 5 ATTORNEYS PAIENIED SEI] 8l973 SHEET 2 0F 5 IELZ- PATENTEU SEP] 8 I975 SHEEI h 0F 5 VORTEX PUMPS REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of my copending application, Ser. No. 104,315, filed Jan. 6, 1971.

FIELD OF THE INVENTION This invention relates to pumps and more particu-' larly to pumps of the type which will be referred to as vortex pumps, which have a toroidal casing formed with an axially offset recess for receiving an open impeller. These pumps are particularly useful for handling solids-bearing liquids.

1 DESCRIPTION OF PRIOR ART The U.S. Pat. to Egger No. 3,171,357, Mar. 2, 1965 discloses a vortex pump, having a recessed impeller in a circular casing with the intersection of the recess with the casing being at substantially 90. The impeller has no recessed eye.

U.S. Pat. to Egger No. 3,316,848, May 2, 1967 (FIG. 3) shows a recessed impeller pump construction like that of the earlier Egger patent. The rear wall of the impeller has secondary vanes.

U.S. Pat. to Sence No. 3,130,679, Apr. 28, 1964 shows a volute casing in FIG. 3. The angle of intersection of the impeller recess with the volute is not shown, but the maximum diameter of the volute is spaced radially outward from the impeller recess at the cutwater.

The impeller has a recessed eye and its vanes are not shrouded, but as seen in FIG. I, the impeller is located within the volute itself.

U.S. Pat. tm'ro'eg'r has found July present 18, 1961 also shows a volute casing with the impeller disposed within the volute itself and with a front cover plate on the impeller.

U.S. Pat. to Brawley No. 2,635,548, Apr. 21, 1953 shows a recessed impeller and an oddly contoured volute casing having an axial inlet (FIGS. 3 and 4). There is substantially no clearance between the impeller and the recess in the casing. The impeller recess intersects the volute in a plane perpendicular to the impeller axis and the outermost portions of the volute wall are radially offset from the impeller recess at the cutwater. The impeller does not have a recessed eye.

Burnside reissue U.S. Pat. No. 24,803, Mar. 29, 1930 shows a solids pump with a volute casing. The major diameter of the volute at the cutwater is greater than the diameter of the impeller recess (FIG. 2). The impeller vanes are shrouded but form a recessed eye.

U.S. Pat. to Glass No. 3,322,070,- May 30, 1967, shows a vortex pump having a cylindrical casing containing the impeller with an axial inlet and a tangential discharge. The casing wall and the impeller recess are of the same diameter. The impeller is widely spaced from the casing wall to provide an auxiliary swirl chambet. The impeller is not shrouded and the inner ends of the impeller vanes form a very small angle with the impeller axis. I

The U.S. Pat. to Schwed et al. No. 3,269,325, Aug. 30, 1966 shows a self-priming vortex-type pump wherein the casing is circumferentially concentric with the impeller. FIG. 2 shows that part of the casing oppo site the discharge throat as having a curved cross section that is less than a semi-circle, but the specification does not describe the casing geometry. There is no recessed impeller eye.

German Pat. No. 179,266, Jan. 16, 1906 shows a combined inlet and impeller concentric with a circular, wherein the impeller has outwardly divergent walls that are tangent to a continuation of the casing wall.

Kay U.S. Pat. No. 1,650,873, Nov. 29, 1927, shows a rotary blower having 12 blades. The specification does not give dimensions of the parts.

The U.S. Pat. to Lykken No. 1,893,710, Jan. 10, 1933 shows a radial flange impeller with the axially outer ends of the vanes normal to the impeller axis and terminating short of the hub to form an impeller eye. The inner ends of the vanes are straight. The impeller is not in a recess to one side of the volute.

LaBouri U.S. Pat. No. 2,669,938, Feb. 23, 1954, shows a spoked impeller with slanted outer edge vanes terminating in inclined, straight inner edges.

The U.S. Pat. to Pray, .lr. No. 2,958,293, Nov. 1, 1960 shows a solids pump wherein the impeller recess is conical, the impeller vane ends are shrouded, and the impeller has no recessed eye. There is no volute and the pump casing is circular having a U-shaped crosssection, even at the cutwater.

The U.S. Pat. to Judd No. 3,319,573, May 16, 1967 shows a centrifugal pump, the casing of which has a volute that increases in depth and volume in an axial direction only and never has a radius greater than that of the impeller recess. The impeller itself has a full diameter convex nose and hence has no recessed eye.

Swiss Pat. No. 390,688 of Aug. 13, 1963 shows a vortex pump with a recessed impeller that makes a close, labyrinth fit with the impeller recess. No front elevation is provided but it appears that upstream of the discharge duct the casing wall substantially forms an extension of the impeller recess. The radial outer wall of easing does not lie in a plane, being closer to the impeller adjacent the outlet than at a point about from the outlet. There is no skew or helical line of intersection between the impeller recess and the volute, assuming the latter to be present. The casing has a radial inner side wall opposite the discharge duct, with a cylindrical peripheral wall. The impeller vanes are shrouded and the impeller has a convex nose rather than a recessed eye.

A paper entitled Some Performance Characteristics of a Centrifugal Pump with Recessed Impeller by V.M. Lubieniecki was received at the ASME headquarters, at 345 East 47th Street, New York, on Nov. 24, 1971. The pump tested was a vortex pump with unshrouded impeller vanes that closely fits the impeller recess and a recessed eye. The casing was concentric with the impeller recess, and hence was not a volute. The conclusions were that deeper vane impellers provide better performance than shallow vane impellers for a given impeller diameter. It was also found that the gallons/minute delivery of a given pump operating at a given speed is directly'proportioned to the square of theimpeller diameter.

SUMMARY OF THE INVENTION The vortex pump of the invention is particularly useful in pumping liquid transportable solids which would be damaged by excessive impeller contact and fluids containing large, stringy or abrasive solids, such as sewage. Although such pumps are generally known in prior art and have been available to the trade, the present invention represents improvements over known pumps of this type, particularly with relation to pump efficiency, the pump head at both low and high discharge volumes and the noise level.

It has been found that the above pump factors and others can be either improved or possibly rendered less desirable by various individual and combination changes in the relatively large number of pump design factors, most of which heretofore have been given only superficial consideration. At the present state of the art, improvements in pump efficiency (for example) which represent gains in only a few percentage points are considered to be of considerable economic value. Some of the design factors which have been found to have significant effects on pump performance are as follows:

The relative radial position of the impeller recess and the internal toroidal wall of the casing volute, particularly at the cutwater.

The angle of intersection between the impeller recess and the volute, particularly at the cutwater.

The radial clearance between the impeller and the impeller recess in the casing.

The c depth of the impeller blades as a function of the discharge diameter (the nominal pump size).

The diameter of the impeller eye relative to pump size.

The discharge angle of the impeller blades.

The number of impeller blades relative to pump size.

The shape of the axial inlet.

Information that will facilitate production of improved pump designs within certain discharge port size ranges is given in the detailed specification which follows. However, and by way of example, one characteristic of the present invention can be explained briefly in this summary and that is the geometry of the impeller recess with respect to the casing volute. It has been found that increased performance is obtainable if the volute itself is made shallower than usual. More specifically, the volute has the same basic cross-sectional radius throughout its working periphery. The radius of the impeller recess is equal to the smallest maximum radius of the volute, which is the maximum radius of the volute at the cutwater so that the intersection of the impeller recess with the volute wall at this angular location is radially of the cross sectional center of curvature of the volute. This means that the impeller recess intersects the volute wall at an obtuse angle substantially around the volute. This also means that the intersection of the impeller recess with the volute wall describes an approximate helix and hence, with the aforesaid obtuse angle of intersection increasing from the tangential zone of discharge (large maximum radius portion of the volute) to an angle of about 180 at the cutwater (small maximum radius portion of the volute).

As mentioned, this and a number of other design features will be best understood from a detailed description of a preferred embodiment of the invention that follows.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an axial cross section through a pump embodying the invention.

FIG. 1A is a fragmentary enlarged view through the tip of the impeller blades and the casing.

FIG. 2 is a section taken on line 22 of FIG. 1.

FIG. 3 is a section taken on line 3--3 of FIG. 2.

FIG. 4 is a view like FIG. 2 with the impeller removed illustrating certain geometrical relationships of the volute.

FIG. 4A is a diagram showing the location of certain nominal radaii of the volute wall.

FIG. 4B is a table showing the centers of the radii of FIG. 4A.

FIGS. 4C and 4D are sections of the pump casing taken as indicated on FIG. 4.

FIGS. 5-9 are sections of the volute wall taken as indicated on FIG. 4 (FIG. 7 shows in dotted lines a volute section having inferior operation for purposes of comparison).

FIG. 10 is a view of the impeller like that of FIG. 2 showing certain geometrical relationships relative to blade shape.

FIG. 11 is a section taken on line 1 1 1 1 of FIG. 10.

FIG. 12 is a section through the impeller showing other geometrical relationships of the construction.

DETAILED DESCRIPTION GENERAL DESCRIPTION OF THE PUMP Referring to FIGS. 1 and 2, the pump embodying the present invention is illustrated generally at 10. The pump has a main casing indicated generally at 12 with an impeller 14 in the casing. In the construction shown, the casing 12 is formed of two major parts, a main section 16 and a backplate section 18. The main section 16 includes a radial front wall 20 having an inlet opening 21 having a diameter indicated at a. An inlet pipe 22 is bolted to the front wall 20 by bolts 23 and has an inlet bore 24 that forms a prolongation of the pump inlet opening 21. At the impeller side of the main casing section 16 a radial flange 26 receives bolts 28 that mount the rear casing section 18.

The pump casing is formed as a volute having a toroidal inner wall 30 which wall, in the preferred construction, has a circular cross section, with the radius of the circular cross section of the volute 30 being designated 2 in the drawings.

The pump casing has a tangential discharge or outlet 31 with a bore 32 having a diameter b that is preferably substantially the same as the diameter a of the pump inlet. In some designs the inlet may be larger than the outlet. The outermost portion 34 of the outlet 31 joins the wall of the volute at 36 (FIG. 2) and forms a smooth, tangential continuation of that portion of the volute wall 30. The opposite wall 38 of the discharge 31 leads from what is termed the cutwater portion or terminal end 39 of the toroidal volute wall 30.

A recess 40 extends rearwardly from the volute wall 30 for receiving the impeller 14. The recess has a diameter R which is about a half inch greater (for example) than the diameter T of the impeller 14 (FIG. 1). As will be described in detail presently, it is a feature of the present invention that the impeller recess 40 intersects the volute wall in an approximately helical plane, illustrated at 41 and best seen in FIGS. 4C and 4D. Also, the radius of the impeller recess 40 is substantially equal to the smallest maximum radius of the casing wall 30 at the cutwater (FIG. 4).

As seen in FIG. 1, the impeller 14 is secured to a stepped shaft 50 by a key 52 and a nut 54. The shaft extends through packings 56in the back plate 18 of the casing and which may be taken up by a gland 58. The shaft is supported in a bearing housing 60 secured by bolts 62 to the backplate 18. The bearing housing 60 the shaft 50 is keyed at 68 to receive a driving pulley or the like (not shown) for rotating the impeller. VOLUTE GEOMETRY Salient features of the volute geometry are illustrated in FIGS. 4-9. As previously described, the cross sectional radius e of the volute-is constant around its peripheral extent, and hence the section is circular. se-

lected layout radii of the volute are illustrated in FIG. 4 between the cutwater radius to the largest layout radius c at the tangent point 36 of the volute with the outlet wall 34 of the discharge. FIGS. 4A and 4B give typical design data. In the illustrated embodiment, the dimensions a and b for the inlet and outlet pipes are 4 inches. The table 'of FIG. 4B taken with the diagram of FIG. 4A shows how to lay out the centers on Cartesian coordinates for the various volute layout radii 01 to c4 relative to the central axis z. This procedure for laying out a volute is well known to pump designers and described in detail in the article How to Lay Out Centrifugal Pump Volute Casings by Edward G. Hilficker in Machine Design, Aug., 1951, pages 137 to 142.

Referring to FIG. 4 it will be noticed that an important feature of the invention is that the minor radius c of the outermost radial portion of the volute wall 30 substantially coincides with the radius of the impeller recess 40 at the cutwater portion 39 of the volute. FIGS. 4C, 4D and 9 show this also.

FIGS. 5-8 are successive transverse sections showing the intersection of the impeller recess 40 with the volute cross section 30. This construction forms an important feature of the present invention in providing an increased efficiency of the pump with a decreased noise level. Starting with the section of FIG. 5, at the tangent point 36 between the volute wall and the discharge wall 34 (FIG. 4) it can be seen that the wall of the impeller recess 40 forms an obtuse angle A with a tangent to the circular are e of the volute. The intersection 41 of the impeller recess and the volute section radius e is best seen in FIGS. 4C and 4D, and it is a feature of the invention that this intersection lies in a skew plane. Referring back to FIG. 5, the angle A is obtuse because the zone of the intersection 41 of the impeller recess 40 and the inner wall 30 of the volute lies radially outside the center of curvature of the radius "e" of the volute. In the detailed example presented, the angle A at the section of FIG. 5 is about 102.

Progresing around the volute from the tangent zone 36 of the discharge toward the cutwater zone 39, it can be seen that the obtuse angle A increases steadily. For example, in FIG. 5, the angle A is equal to approximately 102 in the present embodiment; in FIG. 6 the angle A-is 1 18; in FIG. 7, the angle is 133; in FIG. 8 the angle is 155 and in FIG. 9 (at the cutwater) the angle is 180. Thus, at the cutwater, the impeller recess 40 is substantially tangent to the wall 30 of the volute.

FIG. 7 shows in dotted lines an inferior construction presented for comparison with that of the present invention.

In FIG. 7, as shown in dotted lines, the volute wall,

30a is of constant width around the volute. In other words, the intersection 41a of the impeller recess 40 with the volute wall 30a would be axially spaced from the center of curvature of volute by a distnace equal to the radius e. This construction, which widens the volute, is found to be less efficient than that of the preferred fon'n of the invention illustrated in FIGS. 5-9. IMPELLER CONSTRUCTION In addition to improving the performance of the pump over that of prior known pumps of the recessed impeller type by improving the casing design, it has been found that improvements can be made in the geometry of the impeller itself to increase the efficiency and reduce the noise of the pump. By way of example, a specific pump impeller is described and illustrated in FIGS. 10-12. As seen in FIGS. 10 and 12 the impeller has a keyed hub 42, tapered radial flange portion 43 and a straight radial flange portion 44. The impeller blades 46 project axially from the flange portions 43,44 and they are curved so that their convex faces are their leading faces. The blades 46 have curved inner edges 48, forming a recessed eye. The edges 48 extend in continuous lines axially and radially outward from the base flange. Vanes 49 project from the rear side of the impeller flange portion 43,44 (see also FIG. 2). The number N of impeller blades 46 is somewhat greater than that. indicated by the prior art, and as will be seen presently it has been found that there is a generally optimum number of blades for maximizing impeller efficiency and minimizing the noise level.

FIG. 10 illustrates one manner for generally laying out the curvature of the impeller blades 46. In the design shown, the blades are at three radii that merge smoothly, but each radius is struck from a different circular centerline. For example, the three circular centerlines l, m and n are illustrated, together with the corresponding radius of 0, p and q struck from these centerlines respectively. In the typical pump being described wherein the inlet and outlet throats a and b have a 4 inchdiameter, the dimensions for the radaii centerlines and their length is given in the table of FIG. 10A. Other design factors of the impeller including its major diameter T previously mentioned are given in FIG. 12.

In thetypical construction shown in FIG. 12, the impeller blades 46 have an axial width or depth g that bears a predetermined relation to the other dimensions of theimpeller. The eye 48 formed by the curved inner edges of the vanes 46 of the impeller has a diameter h and the inner vane edges 48 are each formed on a radius k. The coordinates for the radius k are given as an axial coordinate i and a radial coordinate j. In the 4 inch discharge pump being described k equals 7 inches, i equals 5% inches and j equals 3-1/16 inches. The blade depth g in the example given is 2 inches and the major impeller diameter j is 11 k inches. In the example given and as shown in FIG. 10, the number of blades N is 12 with a discharge angle B of just under The radial clearance between the periphery of the impeller 14 and the impeller recess 40 in the pump housing is about 7/16 of an inch.

Table I gives various vortex pump design data for a discharge throat b at the range of about 2 inches to 4 inches and is self-explanatory. Also included is Table Table I Vortex Pump Design Data (b 2 inches to 4 inches) 'b Volute discharge diameter inches N Number of Impeller vanes B Impeller vane discharge angle degrees f Maximum impeller diameter inches g Impeller vane depth inches h Impeller eye diameter inches R Impeller recess diameter inches C Volute radius at cutwater inches e Volute sectional radius inches s Volute spiral severity radial inches/degree N (b 12.3 inches) V tan B/2 (toclosest whole number :10 percent) g F/2+ l inches :10 percent c =(f+ 0.3b 0.25 inch/2) :10 percent f= 6.75 inches b :10 percent h 5 inches 0.25b percent c R/2 or R s =(0.005 inch radial growth/One degree angular increment) percent Typical RPM, tt; 2,400.

Application of the design formulas of Table I will provide a high efficiency pump with the desired headflow rate characteristics for pumps used in sewage work or the like, the formulas given for f (maximum impeller diameter) and for c (radius to volute cutwater) produced better results when applied to pumps having a discharge diameter b of about 2 inches to 4 inches than when applied to larger pumps wherein b" is 6 inches to 10 inches. This does not mean that application of the formulas to Table I to the larger pumps will not serve as a positive-and clear guide to designing these pumps for better characteristics than heretofore attainable (based on the specific prior art design teachings known at this time) without a lengthy, costly and carefully controlled test program. The fact is that formulas which give slightly better results for the larger pumps (6 10 inches) and which also apply to the 4 inches and smaller pumps have been developed and are now preferred.

These alternate and preferable (particularly for the larger pumps) formulas are:

Table III f= 9 inches 0.625 b :10 percent c =(f+ 0.0625b 0.625 inch/2) :10 percent The remaining formulas of Table I continue to apply.

Some explanations relating to the design formulas and the various individual physical pump dimensions that must be selected for the basic desiderata at hand will now be presented. These explanations are backed up by a large number of controlled laboratory tests.

' l. The volute discharge diameter b is determined by the limiting pipe flow velocities resulting from the flow rate desired, this being the usual practice in selecting this factor in the design of centrifugal pumps.

2. For pump applications commonly encountered in the field of pumping sewage or other solids-carrying fluids, the maximum impeller diameter f is ideally determined by the formulas given in Tables I and III, preferably the latter. These formulas apply best to pump designs conventionally known as medium" head pumps. In thosecases where a considerably higher or lower head is required than can be obtained by the reasonable and usual shaft speed (e.g., 1,750 rpm) with the nominal impeller diameter, the diameter f can be changed in accordance with known centrifugal pump affinity laws. For example, to obtain lower head, j must be decreased in proportion to the ratio of the square root of the desired lower head and the square root of the head attained with a pump having the diameter f as given by the formula.

To obtain a higher head pump, f must be increased in proportion to the ratio of the square root of the desired higher head and the square root of the head attained with a pump having the diameter as given by the formula.

Of course, the other dimensions of the pump that are directly or indirectly based on the diameter f will correspondingly change with the modified value of in application of the formulas.

3. Table II shows that the impeller discharge vane angle B may be varied from about 20 to about In selecting the vane angle, it should be recognized that the lower angles give a steeper head-capacity curve (a desirable feature for the type service under consideration) but somewhat less efficiency. The higher vane angles (approaching radial) improve the efficiency of the pump but flatten the head-capacity curve. If too high a vane angle is selected, the pump becomes unfit for solids pumping service. The preferred angle of the vanes is about 30 to 45, depending upon the steepness desired for the head-capacity curve and the efficiency required.

4. The value for the impeller eye diameter h" given in Table I optimizes several factors. It accommodates trimming of the outside diameter 1 of the impeller for performance variations while maintaining full capacity of the impeller. This maintains maximum pump efficiency and extends the flow rate at which the efficiency begins to drop. It also decreases or eliminates leading edge cavitation of the impeller, reduces noise and maintains a reasonably good head-capacity curve slope.

5. As to selecting the number of vanes, generally speaking, the largest number of impeller vanes that can be crowded into the impeller without choking off the impeller inlet at the eye because of vane thickness is recommended. The number of vanes selected also depends on the blade entrance angle and the impeller eye diameter h. With the impeller entrance angle and the impeller exit angle held equal, and where the impeller eye diameter h" is determined in accordance with Table I, the equation for the number of blades N given in Table I will provide the optimum number of vanes for the pump propeller.

6. The impeller vane depth g" is related to the desired flow rate of the pump. However, under the design principles of the present invention, it is assumed that the size of discharge diameter b has already been determined by the expected flow rate and hence, in accordance with Table I the vane depth g is made dependent on b.

7. As to the radius 0 from the centerline to the volute cutwater (FIG. 2) it has been found, under the present invention, that this is a very important variable.

Testshave proven that a smaller radius than has previously been used provides improved results. Accordingly, the formula for the cutwater radius 0" given in Tables I and III represent a valuable contribution to vortex pump design.

8. It will be noted in Table I that the impeller recess diameter R is equal'to one-half the radius of c to the volute cutwater. A number of tests have proven that this results in optimum pump efficiency. It has further been found that holding to this relationship between R and c is of the most importance when maximum diameter impellers (f) are employed.

9. The cross sectional volute radius e is conventionally a constant radius equal to the radius of the discharge diameter b" for the passage of large solids. Tests have shown that the wider volute resulting from using a larger value for the radius e results in reducing the pump efficiency. On the other hand, although use of a smaller radius e would enhance pump efficiency, it would preclude the passage of large solids.

It is noted that in the embodiment of the pump described, the radius e is that of a circle, which geometry was originally set up in the industry under the mistaken belief that a helical flow is superposed on the toroidal flow existing in the pump. However, it has been found that this is not the case and accordingly if a cross-sectional volute shape other than that of a geometric circle is desired for conveniences in casting manufacture or appearance, little performance ,willbe lost so long as the volute width criteria outlined above are maintained. Thus, a somewhat rectangular volute erally radial flange and rotatable in said recess; the improvement wherein the peripheral casing wall is a volute, the entire internal wall of said volute having a smooth arcuate cross sectional shape with corresponding parts of the volute wall having substantially the same shape around the volute, said impeller recess intersecting said volute wall at an obtuse angle substantially around the volute, said intersection lying in a skew plane with the obtuse angle of intersection progressively increasing around the volute from the deepest portion of the volute at the tangential outlet wall to the shallowest, cutwater portion of the volute at the diametrically opposite outlet wall, said radial outer casing wall lying substantially in a plane that is equidistant from the impeller, said impeller having a substantial radial clearance with said recess, the radially inner ends of the impeller vanes being unshrouded to form a recessed eye.

2. The vortex pump of claim 1, wherein said angle of intersection at the cutwater portion of the volute is not substantially less than 180, rendering the recess wall substantially tangent to the toroidal inner wall of said casing at the cutwater.

3. The vortex pump of claim 1, wherein theradially inner ends of the impeller vanes form substantially continuous lines that extend axially and radially outward cross section having ample fillets can be employed, or

an oval section can be employed, so long as the cross sectional area and volute widths are maintained in accordance with the formulas herein given.

As to the volute severity, which is the radial change in radius of the periphery of the volute per degree of angular position, this quantity s is given inTable I. For most applications in pumping the sewage and other solids, this is the optimum value. The selection of a more severe volute flattens and lowers the headcapacity curve, particularly at shut-off and decreases both peak efficiency and efficiency of lower flow rates. On the other hand, changing to a less severe (rounder) volute has similar effects except that here there is a slight increase in low flow rate efficiency.

As previously described, it as been ound under the resent invention that a recessed impeller, vortex pump will have optimum efficiency, a head-capacity curve suitable for the pumping of solids, a low noise level, will require a minimum horsepower for a given head and will maintain a good pressure curve over the operational range of pump speeds.

Although the best mode contemplated for carrying out the present invention has been herein shown and.

described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention.

What I claim is:

l. A vortex pump of the type having a casing formed with a generally toroidal peripheral wall and a radial outer wall, an axial inlet for the casing in said radial outerwall, a cylindrical impeller recess formed in the casing opposite said inlet and joining the inner periphery of said volute, an outlet having one'wall leading tangentially from said casing and an impeller with periph- 'erally unshrouded vanes projecting axially from a genfrom the impeller flange.

4. The vortex pump of claim 2, wherein R is substantially equal to 20, where R= the diameter of the impeller recess in inches, and

c the radius of the volute at the cutwater in inches.

5. The vortex pump of claim 4, wherein b =fil10uj 2 inches to 10 inches, and

g b/2) i 1 inches :10 percent, where b diameter of the casing outlet in inches. g axial depth of the impeller vanes in inches. 16. The'vortex pump of claim 4, wherein b about 2 inches to 10 inches, f 9 inches 0.625b :10 percent, and c (f 0.0625b 0.625 inch/2) :10 percent, where b Diameter of the casing outlet in inches.

f Impeller diameter in inches, and

c Volute radius to the cutwater in inches,

b =-Diameter of the casing outlet in inches. 7. The vortex pump of claim 6, wherein h 5 inches 0.25b ilO percent, where h the impeller eye diameter. 8. The vortex pump of claim 4, wherein b about 2 inches to 10 inches, N (b 12.3) \Vtan 8/2 to the closest whole number, :tlO percent, where b Diameter of the casing outlet in inches, N Number of impeller blades, B impeller vane discharge angle of about 20 to 9. The vortex pump of claim 8, wherein B, the impeller vane discharge angle, is about 30 45.-

10. A vortex pump of the type having a casing formed with a generally toroidal lntemal wall, an axial inlet for the casing, a cylindrical impeller recess formed in the casing opposite said inlet and joining the inner periph cry of said volute, an outlet having one wall leading tangentially from said casing and an impeller with peripherally unshrouded vanes projecting axially from a flange and rotatable in said recess; the improvement wherein the internal casing wall is a volute, the entire internal wall of said volute having a smooth cross sectional shape around the volute, said impeller recess intersecting said volute wall at an obtuse angle substantially around the volute, with the obtuse angle of intersection progressively increasing around the volute from its smallest value at the deepest portion of the volute at the tangential outlet wall to its largest value at the shallowest, cutwater portion of the volute at the diametrically opposite outlet wall, said impeller having a substantial radial clearance with said recess, the radially inner ends of the impeller vanes extending axially and radially outward from said impeller flange and being unshrouded to form a recessed eye, the value of R being substantially equal to 20, where R the diameter of the impeller recess in inches, and c the radius of the volute at the cutwater in inches.

11. The vortex pump of claim 10, wherein b about 2 inches to inches and g= (Vb [2) l inches :10 percent, where b diameter of the casing outlet in inches. 3 axial depth of the impeller vanes in inches. 12. The vortex pump of claim 10, wherein b about 2 inches to 10 inches, f 9 inches 0.62512 :10 percent, and c (f+ 0.0625b 0.625 inch/2) :10 percent, where b Diameter of the casing outlet in inches. f Impeller diameter in inches, and c Volute radius to the cutwater in inches, b Diameter of the casing outlet in inches. 13. The vortex pump of claim 12, wherein h F 5 inches 0.25b 10 percent, where h the impeller eye diameter. 14. The vortex pump of claim 10, wherein b about 2 inchesmlinches, N (b 12.3) tan 8/2 to the closest whole number, :10 percent, where b Diameter of the casing outlet in inches, N Number of impeller blades, B Impeller vane discharge angle of about 20 to 15. The vortex pump of claim 14, wherein B, the impellet vane discharge angle, is about 30 45.

I I l i I zgfl gg UNITED STATES PATENT OFFICE V 1 I CERTIFICATE OF CORRECTION Patent No. 3,759,628 Dated Se tember 1 19 Lventofls) DENNIS D. KEMPF 7 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Abstract, last line, change "of" (second occurrence) to to Col. 1, line 34 after "Draeger" delete "has found July present 18, 1961' and insert 2 ,992,6l7, July 18, 1961 Col. .3, line 24', change "0" to axial Col. 5, line 52, change "progresing" to progressing C91. 6, line 1, change 'distnac e" to dietance Col. 7, line 8, change "C" to (lower case c Col. 7, line 11, change "''\/tan 5 to tan Col. 7, line .13, change b/2" to gr".

Col. 10 line 34, changeb/2) to 'Col. 11, line 18, change b/Z to Signed and sealed'this 15th day of October 1974,

(SEAL) Attest: H

MCCOY M. GIBSON JR. I c. MARSHALL DANN Attesting Officer I vCouunissioner of Patents 

1. A vortex pump of the type having a casing formed with a generally toroidal peripheral wall and a radial outer wall, an axial inlet for the casing in said radial outer wall, a cylindrical impeller recess formed in the casing opposite said inlet and joining the inner periphery of said volute, an outlet having one wall leading tangentially from said casing and an impeller with peripherally unshrouded vanes projecting axially from a generally radial flange and rotatable in said recess; the improvement wherein the peripheral casing wall is a volute, the entire internal wall of said volute having a smooth arcuate cross sectional shape with corresponding parts of the volute wall having substantially the same shape around the volute, said impeller recess intersecting said volute wall at an obtuse angle substantially around the volute, said intersection lying in a skew plane with the obtuse angle of intersection progressively increasing around the volute from the deepest portion of the volute at the tangential outlet wall to the shallowest, cutwater portion of the volute at the diametrically opposite outlet wall, said radial outer casing wall lying substantially in a plane that is equidistant from the impeller, said impeller having a substantial radial clearance with said recess, the radially inner ends of the impeller vanes being unshrouded to form a recessed eye.
 2. The vortex pump of claim 1, wherein said angle of intersection at the cutwater portion of the volute is not substantially less than 180*, rendering the recess wall substantially tangent to the toroidal inner wall of said casing at the cutwater.
 3. The vortex pump of claim 1, wherein the radially inner ends of the impeller vanes form substantially continuous lines that extend axially and radially outward from the impeller flange.
 4. The vortex pump of claim 2, wherein R is substantially equal to 2c, where R the diameter of the impeller recess in inches, and c the radius of the volute at the cutwater in inches.
 5. The vortex pump of claim 4, wherein b about 2 inches to 10 inches, and g Square Root (b/2) + 1 3/8 inches + or - 10 percent, where b diameter of the casing outlet in inches. g axial depth of the impeller vanes in inches.
 6. The vortex pump of claim 4, wherein B about 2 inches to 10 inches, f 9 inches + 0.625b + or - 10 percent, and c (f + 0.0625b + 0.625 inch/2) + or - 10 percent, where b Diameter of the casing outlet in inches. f Impeller diameter in inches, and c Volute radius to the cutwater in inches, b Diameter of the casing outlet in inches.
 7. The vortex pump of claim 6, wherein h 5 inches + 0.25b + or - 10 percent, where h the impeller eye diameter.
 8. The vortex pump of claim 4, wherein b about 2 inches to 10 inches, N (b + 12.3) Cube Root tan B/2 to the closest whole number, + or - 10 percent, where b Diameter of the casing outlet in inches, N Number of impeller blades, B Impeller vane discharge angle of about 20* to 75*
 9. The vortex pump of claim 8, wherein B, the impeller vane discharge angle, is about 30* - 45*.
 10. A vortex pump of the type having a casing formed with a generally toroidal internal wall, an axial inlet for the casing, a cylindrical impeller recess formed in the casing opposite said inlet and joining the inner periphery of said volute, an outlet having one wall leading tangentially from said casing and an impeller with peripherally unshrouded vanes projecting axially from a flange and rotatable in said recess; the improvement wherein the internal casing wall is a volute, the entire internal wall of said volute having a smooth cross sectional shape around the volute, said impeller recess intersecting said volute wall at an obtuse angle substantially around the volute, with the obtuse angle of intersection progressively increasing around the volute from its smallest value at the deepest portion of the volute at the tangential outlet wall to its largest value at the shallowest, cutwater portion of the volute at the diametrically opposite outlet wall, said impeller having a substantial radial clearance with said recess, the radially inner ends of the impeller vanes extending axially and radially outward from said impeller flange and being unshrouded to form a recessed eye, the value of R being substantially equal to 2c, where R the diameter of the impeller recess in inches, and c the radius of the volute at the cutwater in inches.
 11. The vortex pump of claim 10, wherein b about 2 inches to 10 inches and g Square Root (b/2)+ 1 3/8 inches + or - 10 percent, where b diameter of the casing outlet in inches. g axial depth of the impeller vanes in inches.
 12. The vortex pump of claim 10, wherein b about 2 inches to 10 inches, f 9 inches + 0.625b + or - 10 percent, and c (f + 0.0625b + 0.625 inch/2) + or - 10 percent, where b Diameter of the casing outlet in inches. f Impeller diameter in inches, and c Volute radius to the cutwater in inches, b Diameter of the casing outlet in inches.
 13. The vortex pump of claim 12, wherein h 5 inches + 0.25b + or - 10 percent, where h the impeller eye diameter.
 14. The vortex pump of claim 10, wherein b about 2 inches to 10 inches, N (b + 12.3) Cube Root tan B/2 to the closest whole number, + or - 10 percent, where b Diameter of the casing outlet in inches, N Number of impeller blades, B Impeller vane discharge angle of about 20* to 75*
 15. The vortex pump of claim 14, wherein B, the impeller vane discharge angle, is about 30* - 45*. 